Sub-assembly mounting system

1. A method for mounting a module across a pair of frame rails of a motor vehicle chassis, the method comprising the steps of:

mounting a pair of side rail brackets longitudinally aligned on one another on outside faces of the frame rails, each of the side rail brackets having a horizontal back edge extending above a top face of its respective frame rail and two alignment arms extending outwardly from the frame rail and perpendicular thereto;

providing four mounting tabs on the module, each mounting tab extending downwardly from the module in a usual orientation of the module, the mounting tabs being disposed at the four corners of a rectangle with each mounting tab having a lead cam section and an alignment edge;

lowering the module onto the pair of frame rails in an orientation bringing each of the four mounting tabs into proximity to a different one of the alignment arms, with the alignment edges guiding side to side positioning of the module by interaction against the frame rails and the lead cam sections guiding positioning of the module fore to aft by contact with the alignment arms; and

resting the module on the horizontal back edge of the side rail bracket to complete alignment of the alignment arms and the mounting tabs.

2. A method for mounting a module as set forth in claim 1 , further comprising the step of:

attaching the mounting tabs and side rail brackets using conventional fastening means.

3. A method for mounting a module as set forth in claim 2 , further comprising the steps of:

assembling the module prior to installation on the vehicle chassis from a carrier and a fuel tank.